A predictive numerical tool for invasive species monitoring and management: rugulopteryx okamurae as a case study

Since its first detection on the coast of the Strait of Gibraltar in 2015, the exotic brown alga Rugulopteryx okamurae has spread explosively over a large part of the Atlantic and Mediterranean coasts, with severe impacts on established benthic communities, fisheries and tourism. The impact of the algae in the Mediterranean environment has recently been the subject of extensive research, but key aspects of the invasion, including its distribution and the underlying causes of its success, remain unknown. To gain insight into the spread and establishment of the species, a high-resolution three-dimensional hydrodynamic model coupled with a Lagrangian algorithm is used, with virtual tracers representing free spores, thalli fragments or detached mats of Rugulopteryx okamurae. The hindcast of the passive spread of the algae in 2021, as a test year, indicated a predominantly eastward direction, with transport by the Atlantic jet entering the Alboran Sea being the most influential physical mechanism. The potential utility of numerical tools in elucidating the dispersal dynamics of introduced and expanding species, identifying high-risk areas and formulating management strategies for this species is discussed.